Chronic social defeat alters brain vascular-associated cell gene expression patterns leading to vascular dysfunction and immune system activation

Abstract

Brain vascular integrity is critical for brain health, and its disruption is implicated in many brain pathologies, including psychiatric disorders. Brain-vascular barriers are a complex cellular landscape composed of endothelial, glial, mural, and immune cells. Yet currently, little is known about these brain vascular-associated cells (BVACs) in health and disease. Previously, we demonstrated that 14 days of chronic social defeat (CSD), a mouse paradigm that produces anxiety and depressive-like behaviors, causes cerebrovascular damage in the form of scattered microbleeds. Here, we developed a technique to isolate barrier-related cells from the mouse brain and subjected the isolated cells to single-cell RNA sequencing. Using this isolation technique, we found an enrichment in BVAC populations, including distinct subsets of endothelial and microglial cells. In CSD compared to non-stress, home-cage control, differential gene expression patterns disclosed biological pathways involving vascular dysfunction, vascular healing, and immune system activation. Overall, our work demonstrates a unique technique to study BVAC populations from fresh brain tissue and suggests that neurovascular dysfunction is a key driver of psychosocial stress-induced brain pathology.

Amplified Microglial Dysfunction and Brain Lesions in Mouse Models for Comorbidity of Chronic Stress and Intracerebral Hypoperfusion

“…Although disruption of the NVU has been associated with chronic stress, the exact effects remain disputed. Some studies in the literature suggest that chronic stress leads to BBB dysfunction [24][25][26][27][28][29][30][31][32]. For example, one study reported scattered deposition of plasma immunoglobulins and erythrocytes in the brain following exposure to chronic social defeat stress, indicating the occurrence of cerebrovascular microhemorrhages [28].…”

“…In recent years, both clinical and preclinical studies have suggested that the disruption of the NVU may serve as a potential neuropathological link between chronic stress and depression [24][25][26][27][28][29][30][31][32]. For instance, studies in the model of chronic social defeat stress (CSDS) have shown a decrease in the expression of Claudin-5 (Cldn5) in the nucleus accumbens (Nac).…”

“…However, it's important to acknowledge that the relationship between chronic stress and NVU remains a topic of ongoing debate. Some studies have reported mild neuropathological and molecular changes in the NVU after chronic stress [24][25][26][27][28][29]. Moreover, one study has failed to observe damage to BBB permeability after chronic stress [33].…”

Stress-induced dysfunction of neurovascular astrocytes contributes to sex-specific behavioral deficits

“…This included decreased levels of S100b (F (1,25) =22.56, p<0.0001) and Aqp4 transcripts (F (1,25) =7.960, p=0.009). Virally mediated knockdown of Aqp4 also reduced expression levels of S100b and Aqp4, alongside Megf10 (F(1,25) =6.647, p=0.016) and Vegf (F(1,25) =6.311, p=0.019) in the frontal cortex. Together, these data indicate that transcripts reflecting the phenotype of astrocytes shift prior to the emergence of stress-induced deficits in behavior, and that depletion of Aqp4 in PFC astrocytes is sufficient to disrupt markers of astrocyte identity (i.e., S100b) and function (i.e., Megf10, Vegf).AQP4 knockdown in the PFC and sub-CUS induce astrocyte dystrophyA separate cohort of mice received intravascular injections of tomato lectin prior to perfusion and immunostaining (d8), with subsequent analyses focused on astrocyte-blood vessel interaction in the PFC (Fig 5A).…”

“…Alongside pronounced astrocyte dystrophy, recent studies indicate disruption of the neurovasculature in stress. This includes loss of tight junction proteins, reduced cerebral blood flow, and heightened blood-brain barrier (BBB) permeability in select brain regions [9,[23][24][25][26][27][28]. Together, these findings suggest that stressinduced dysregulation of astrocytes at the PFC neurovascular interface leads to behavioral and cognitive consequences.…”